Second-Generation Stent Superior in Clinical Endpoints

Action Points

Explain to interested patients that the decision to undergo a percutaneous coronary intervention and the choice of stent or other device to be used are made based on a clinical assessment of each patient.

Explain to patients that both the everolimus-eluting Xience stent and the paclitaxel-eluting Taxus stent are FDA approved coronary stents.

The everolimus-eluting Xience stent appears superior to the paclitaxel-eluting Taxus stent based on the clinical endpoint of target lesion failure, according to findings from the SPIRIT-IV trial.

A year after treatment, 4.2% of patients who received the Xience stent had target lesion failure, the primary endpoint of the SPIRIT trial, versus 6.8% of patients treated with Taxus stents (P=0.001 for superiority), according to Gregg W. Stone, MD, of Columbia University in New York City.

Moreover, the everolimus-eluting stent was also superior when compared on the basis of ischemia-driven revascularization at one year (P=0.001 for superiority).

Rates of cardiac death and MI in the target vessel were also less in the Xience arm, 2.2% versus 3.2%. Although this confirmed the noninferiority of Xience (P<0.001), these results did not meet the threshold for superiority (P<0.09).

While the overall results clearly favored the everolimus-eluting stent, there was no significant difference in outcomes among a subset of patients with diabetes -- always a difficult group in stent trials.

Moreover, the rates of target lesion failure among patients with diabetes, 6.4% in Xience group versus 6.9% in Taxus group, did not differ "regardless of whether the patients were insulin-dependent or did not require insulin," Stone and colleagues wrote.

The use of target lesion failure, or TLF, as an endpoint (a composite of cardiac death, target-vessel myocardial infarction, or ischemia-driven target-lesion revascularization) marks an FDA-mandated change in the design of pivotal trials of drug-eluting stents. It's an attempt to more accurately reflect real-world circumstances.

Earlier drug-eluting stent trials used angiographic endpoints to determine efficacy, but in SPIRIT-IV the patients did not have routine follow-up angiography.

The trial enrolled 3,678 patients who were randomly assigned to everolimus or paclitaxel-eluting stents. The average age of patients was 63, and about two-thirds were men.

Xience also had the edge on stent thrombosis, with a rate of 0.3% versus 1.1% for a hazard ratio of 0.27 (95% CI 0.11 to 0.67). But the trial was not powered to confirm superiority for this endpoint, Stone said at TCT.

In an editorial that accompanied the SPIRIT-IV results, Richard A. Lange, MD, and L. David Hillis, MD, of the University of Texas Health Science Center in San Antonio, wrote that design improvements are a likely explanation for the apparent safety and efficacy edge demonstrated by Xience and other second generation drug-eluting stents.

"With the newer drug-eluting stents, everolimus, a semisynthetic sirolimus analogue, is released from a thin coating of a biocompatible polymer on a flexible cobalt-chromium stent frame with thin struts," they wrote.

"In contrast, in the older drug-eluting stents, paclitaxel is released from a proprietary polymer coating affixed to a less flexible stainless steel stent with thicker struts."

But Lange and Hills cautioned that research into cost-effectiveness is still important before physicians routinely switch.

They said investigators should "determine whether the absolute reduction of 1 to 2 percentage points in myocardial infarction (mostly non-ST-segment elevation) and the absolute reduction of 2 to 3 percentage points in target-lesion revascularization" is worth an estimated $300 extra for the Xience stent.

They also noted that "for patients with diabetes (who comprise 20 to 30% of patients undergoing PCI), the less expensive paclitaxel-eluting stent may be appropriate."

SPIRIT IV was supported by Abbott Vascular.

Stone said he served on advisory boards for Abbott Vascular and Boston Scientific.

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